An imide derivative or a salt thereof whose typical example is a compound of formula (8) mentioned later or an acid addition salt thereof is known to be useful as a medicament for treating schizophrenia, senile psychiatric disorder, bipolar disorder, neurosis, etc. (Patent Reference 1). And, some processes for preparing an imide derivative of the following formula (I):
wherein A is optionally substituted C2-4 alkylene group or other, D is carbonyl group or other, Y is optionally substituted C1-2 alkylene group, Z is optionally substituted imino group or other are also reported. For example, Patent Reference 2 discloses a process for preparing the imide derivative of the above-mentioned formula (I) which comprises reacting a compound of formula (II):
wherein A is optionally substituted C2-4 alkylene group or other, and D is carbonyl group or other, and a quaternary ammonium salt of formula (III):
wherein Y is optionally substituted C1-2 alkylene group, Z is optionally substituted imino group or other, X− is a counteranion in the presence of a solid inorganic base and water.
In addition, Patent Reference 3 discloses that the compound of formula (III) can be prepared by reacting a compound of formula (IV):
wherein Z is optionally substituted imino group or other, anda compound of formula (V):
wherein X is a group which can become the above counteranion X− after cleavage, and Y is optionally-substituted C1-2 alkylene group in the presence of potassium carbonate whose specific surface area is less than 1.8 m2/g.
Furthermore, Patent Reference 4 discloses a process for preparing the compound of formula (III) which comprises reacting the compound of formula (IV) and the compound of formula (V) in an organic solvent in the presence of potassium carbonate whose mean particle size (50% D) is not more than 200 μm.
However, these processes have some problems on the preparing processes, for example, the product of formula (I) contains a by-product (hereinafter, referred to as “by-product (R)”), or the reaction time of the preparing processes is unstable. Such by-product (R) might cause the quality loss of the imide compound of formula (I), hence it is necessary to remove the by-product through a purification. Thus, it has been desired to further reduce the producing of by-product (R) and stabilize the reaction time from the viewpoint of the yield of the product and the production cost.